Discovery of chemical elements - Wikipedia

Z Element Observed or predicted Isolated (widely known) Notes Year By Year By 15 Phosphorus 1669 H. Brand 1669 H. Brand Prepared and isolated from urine, it was the first element whose discovery date and discoverer are recorded.^[53] Its name first appears in print in the work of Georg Kaspar Kirchmayer [de] in 1676. Recognised as an element by Lavoisier.^[1] 1 Hydrogen 1671 R. Boyle 1671 R. Boyle Robert Boyle produced it by reacting iron filings with dilute acid.^[54][55] Henry Cavendish in 1766 was the first to distinguish H
₂ from other gases.^[56] Lavoisier named it in 1783.^[57][58] It was the first elemental gas known. 11 Sodium 1702 G. E. Stahl 1807 H. Davy Georg Ernst Stahl obtained experimental evidence that led him to suggest the fundamental difference of sodium and potassium salts in 1702,^[59] and Henri Louis Duhamel du Monceau was able to prove this difference in 1736.^[60] Andreas Sigismund Marggraf again recognised the difference between soda ash and potash in 1758, but not all chemists accepted his conclusion. In 1797, Martin Heinrich Klaproth suggested the names natron and kali for the two alkalis (whence the symbols). Davy isolated sodium metal a few days after potassium, by using electrolysis on sodium hydroxide^[61] and potash^[62] respectively. 19 Potassium 1702 G. E. Stahl 1807 H. Davy 27 Cobalt 1735 G. Brandt 1735 G. Brandt Proved that the blue color of glass is due to a new kind of metal and not bismuth as thought previously.^[63] 20 Calcium 1739 J. H. Pott 1808 H. Davy Lime was known as a substance for centuries, but only in the 18th century was its chemical nature recognised. Pott recognised terra calcarea (calcareous earth) as an individual "earth" in his treatise of 1739. Guyton de Morveau, Lavoisier, Berthollet, and Fourcroy suggested in 1787 that it was the oxide of an element. Davy isolated the metal electrochemically from quicklime.^[1] 14 Silicon 1739 J. H. Pott 1823 J. Berzelius Silicon compounds (rock crystals and glass) were known to the ancients, but its chemical investigation dates only to the 17th century. Johann Joachim Becher (of the phlogiston theory) identified silica as the terra vitrescibilis, and Johann Heinrich Pott recognised it as an individual "earth" in his treatise of 1739.^[1] Silica appears as a "simple earth" in the Méthode de nomenclature chimique, and in 1789 Lavoisier concluded that the element must exist.^[1] Davy thought in 1800 that silica was a compound, not an element, and in 1808 he proved this although he could not isolate the element, and suggested the name silicium.^[64][65] In 1811 Louis-Joseph Gay-Lussac and Louis-Jacques Thénard probably prepared impure silicon,^[66] and Berzelius obtained the pure element in 1823.^[67] The name was proposed to be changed to silicon by Thomas Thomson in 1817, and this was eventually accepted because of its analogies to boron and carbon. 13 Aluminium 1746 J. H. Pott 1824 H.C.Ørsted Paracelsus recognised aluminis as separate from vitriol in 1570, and Andreas Libavius proposed in his 1597 treatise to name the unknown earth of alum alumina. In 1746, Johann Heinrich Pott published a treatise distinguishing alum from lime and chalk, and Marggraf precipitated the new earth in 1756.^[1] Antoine Lavoisier predicted in 1787 that alumina is the oxide of an undiscovered element, and in 1808 Davy tried to decompose it. Although he failed, he proved Lavoisier correct and suggested the present name.^[64][68] Hans Christian Ørsted was the first to isolate metallic aluminium in 1824.^[69][70] 28 Nickel 1751 F. Cronstedt 1751 F. Cronstedt Found by attempting to extract copper from the mineral known as fake copper (now known as niccolite).^[71] 12 Magnesium 1755 J. Black 1808 H. Davy Joseph Black observed that magnesia alba (MgO) was not quicklime (CaO) in 1755; until then, both substances had been confused. Davy isolated the metal electrochemically from magnesia.^[72] 9 Fluorine 1771 W. Scheele 1886 H. Moissan Fluorspar was described by Georgius Agricola in 1529.^[73] Scheele studied fluorspar and correctly concluded it to be the lime (calcium) salt of an acid.^[74] Radical fluorique appears on the list of elements in Lavoisier's Traité Élémentaire de Chimie from 1789, but radical muriatique also appears instead of chlorine.^[75] André-Marie Ampère again predicted in 1810 that hydrofluoric acid contained an element analogous to chlorine, and between 1812 and 1886 many researchers tried to obtain it. It was eventually isolated by Moissan.^[76] 8 Oxygen 1771 W. Scheele 1771 W. Scheele Scheele obtained it by heating mercuric oxide and nitrates in 1771, but did not publish his findings until 1777. Joseph Priestley also prepared this new air by 1774, but only Lavoisier recognized it as a true element; he named it in 1777.^[77][78] Before him, Sendivogius had produced oxygen by heating saltpetre, correctly identifying it as the "food of life".^[79] 7 Nitrogen 1772 D. Rutherford 1772 D. Rutherford Rutherford discovered nitrogen while studying at the University of Edinburgh.^[80] He showed that the air in which animals had breathed, even after removal of the exhaled carbon dioxide, was no longer able to burn a candle. Carl Wilhelm Scheele, Henry Cavendish, and Joseph Priestley also studied the element at about the same time, and Lavoisier named it in 1775–6.^[81] 56 Barium 1772 W. Scheele 1808 H. Davy Scheele distinguished a new earth (BaO) in pyrolusite in 1772. He did not name his discovery; Guyton de Morveau suggested barote in 1782.^[1] It was changed to baryte in the Méthode de nomenclature chimique of Louis-Bernard Guyton de Morveau, Antoine Lavoisier, Claude Louis Berthollet, and Antoine François, comte de Fourcroy (1787). Davy isolated the metal by electrolysis.^[82] 25 Manganese 1774 W. Scheele 1774 J. G. Gahn Distinguished pyrolusite as the calx of a new metal. Ignatius Gottfred Kaim might have isolated it in 1770, but there is uncertainty on that. It was isolated by reduction of manganese dioxide with carbon. Given its present name in 1779 by Guyton de Morveau; prior to that it was called magnesia.^[1][83] 17 Chlorine 1774 W. Scheele 1774 W. Scheele Obtained it from hydrochloric acid, but thought it was an oxide. Only in 1808 did Humphry Davy recognize it as an element.^[84][85] 42 Molybdenum 1778 W. Scheele 1788 J. Hjelm Scheele recognised the metal as a constituent of molybdena.^[86] Before that, Axel Cronstedt had assumed that molybdena contained a new earth in 1758.^[1] 74 Tungsten 1781 W. Scheele 1783 J. and F. Elhuyar Scheele showed that scheelite (then called tungsten) was a salt of calcium with a new acid, which he called tungstic acid. The Elhuyars obtained tungstic acid from wolframite and reduced it with charcoal, naming the element "volfram".^[1][87] Since that time both names, tungsten and wolfram, have been used depending on language.^[1] In 1949 IUPAC made wolfram the scientific name, but this was repealed after protest in 1951 in favour of recognising both names pending a further review (which never materialised). Currently only tungsten is recognised for use in English.^[85] 52 Tellurium 1782 F.-J.M. von Reichenstein 1798 H. Klaproth Muller observed it as an impurity in gold ores from Transylvania.^[88] Klaproth isolated it in 1798.^[85] 38 Strontium 1787 W. Cruikshank 1808 H. Davy W. Cruikshank in 1787 and Adair Crawford in 1790 concluded that strontianite contained a new earth. It was eventually isolated electrochemically in 1808 by Davy.^[89] 5 Boron 1787 L. Guyton de Morveau, A. Lavoisier, C. L. Berthollet, and A. de Fourcroy 1809 H. Davy Borax was known from ancient times. In 1787, radical boracique appeared in the Méthode de nomenclature chimique of Louis-Bernard Guyton de Morveau, Antoine Lavoisier, Claude Louis Berthollet, and Antoine François, comte de Fourcroy.^[1] It also appears in Lavoisier's Traité Élémentaire de Chimie from 1789.^[75] In 1808, Lussac and Thénard announced a new element in sedative salt and named it bore. Davy announced the isolation of a new substance from boracic acid in 1809, naming it boracium.^[90] As the element turned out not to be a metal, he revised his proposal to boron in 1812.^[1] 1789 A. Lavoisier Lavoisier writes the first modern list of chemical elements – containing 33 elements including light and heat but omitting Na, K (he was unsure of whether soda and potash without carbonic acid, i.e. Na₂O and K₂O, are simple substances or compounds like NH₃),^[91] Sr, Te; some elements were listed in the table as unextracted "radicals" (Cl, F, B) or as oxides (Ca, Mg, Ba, Al, Si).^[75] He also redefines the term "element". Until then, no metals except mercury were considered elements. 40 Zirconium 1789 H. Klaproth 1824 J. Berzelius Martin Heinrich Klaproth identified a new oxide in zircon in 1789,^[92][93] and in 1808 Davy showed that this oxide has a metallic base although he could not isolate it.^[64][94] 92 Uranium 1789 H. Klaproth 1841 E.-M. Péligot Klaproth mistakenly identified a uranium oxide obtained from pitchblende as the element itself and named it after the recently discovered planet Uranus.^[95][96] 22 Titanium 1791 W. Gregor 1825 J. Berzelius Gregor found an oxide of a new metal in ilmenite; Klaproth independently discovered the element in rutile in 1795 and named it. The pure metallic form was only obtained in 1910 by Matthew A. Hunter.^[97][98] 39 Yttrium 1794 J. Gadolin 1843 H. Rose Johan Gadolin discovered the earth in gadolinite in 1794. He did not name his discovery, but Andreas Ekeberg did so when he confirmed it in 1797.^[1] Mosander showed later that its ore, yttria, contained more elements.^[99][100] In 1808, Davy showed that yttria is a metallic oxide, although he could not isolate the metal.^[64][101] Wöhler mistakenly thought he had isolated the metal in 1828 from a volatile chloride he supposed to be yttrium chloride,^[102][103] but Rose proved otherwise in 1843 and correctly isolated the element himself that year. 24 Chromium 1797 N. Vauquelin 1798 N. Vauquelin Vauquelin analysed the composition of crocoite ore in 1797, and later isolated the metal by heating the oxide in a charcoal oven.^{[1][104][105]} 4 Beryllium 1798 N. Vauquelin 1828 F. Wöhler and A. Bussy Vauquelin discovered the oxide in beryl and emerald in 1798, and in 1808 Davy showed that this oxide has a metallic base although he could not isolate it.^[64][106] Vauquelin was uncertain about the name to give to the oxide: in 1798 he called it la terre du beril, but the journal editors named it glucine after the sweet taste of beryllium compounds (which are highly toxic). Johann Heinrich Friedrich Link proposed in 1799 to change the name from Glucine to Beryllerde or Berylline (because glucine resembled glycine), a suggestion taken up by Klaproth in 1800 in the form beryllina. Klaproth had independently worked on beryl and emerald and likewise concluded that a new element was present. The name beryllium for the element was first used by Wöhler upon its isolation (Davy used the name glucium). Both names beryllium and glucinium were used (the latter mostly in France) until IUPAC decided on the name beryllium in 1949.^[1] 23 Vanadium 1801 A. M. del Río 1867 H. E. Roscoe Andrés Manuel del Río found the metal (calling it erythronium) in vanadinite in 1801, but the claim was rejected after Hippolyte Victor Collet-Descotils dismissed it as chromium based on erroneous and superficial testing.^[107] Nils Gabriel Sefström rediscovered the element in 1830 and named it vanadium. Friedrich Wöhler then showed that vanadium was identical to erythronium and thus that del Río had been right in the first place.^[108][109] Del Río then argued passionately that his old claim be recognised, but the element kept the name vanadium.^[109] 41 Niobium 1801 C. Hatchett 1864 W. Blomstrand Hatchett found the element in columbite ore and named it columbium. In 1809, W. H. Wollaston claimed that columbium and tantalum are identical, which proved to be false.^[85] Heinrich Rose proved in 1844 that the element is distinct from tantalum, and renamed it niobium. American scientists generally used the name columbium, while European ones used niobium. Niobium was officially accepted by IUPAC in 1949.^[110] 73 Tantalum 1802 G. Ekeberg Ekeberg found another element in minerals similar to columbite, and named it after Tantalus from Greek mythology because of its inability to be dissolved by acids (just as Tantalus was tantalised by water that receded when he tried to drink it).^[85] In 1809, W. H. Wollaston claimed that columbium and tantalum are identical, which proved to be false.^[85] In 1844, Heinrich Rose proved that the elements were distinct and renamed columbium to niobium (Niobe is the daughter of Tantalus).^[111] 46 Palladium 1802 W. H. Wollaston 1802 W. H. Wollaston Wollaston discovered it in samples of platinum from South America, but did not publish his results immediately. He had intended to name it after the newly discovered asteroid, Ceres, but by the time he published his results in 1804, cerium had taken that name. Wollaston named it after the more recently discovered asteroid Pallas.^[112] 58 Cerium 1803 H. Klaproth, J. Berzelius, and W. Hisinger 1826 G. Mosander Berzelius and Hisinger discovered the element in ceria and named it after the newly discovered asteroid (then considered a planet), Ceres. Klaproth discovered it simultaneously and independently in some tantalum samples. Mosander proved later that the samples of all three researchers had at least another element in them, lanthanum.^[113] 76 Osmium 1803 S. Tennant 1803 S. Tennant Tennant had been working on samples of South American platinum in parallel with Wollaston and discovered two new elements, which he named osmium and iridium.^[114] 77 Iridium 1803 S. Tennant and H.-V. Collet-Descotils 1803 S. Tennant Tennant had been working on samples of South American platinum in parallel with Wollaston and discovered two new elements, which he named osmium and iridium, and published the iridium results in 1804.^[115] Collet-Descotils also found iridium the same year, but not osmium.^[85] 45 Rhodium 1804 H. Wollaston 1804 H. Wollaston Wollaston discovered and isolated it from crude platinum samples from South America.^[116] 53 Iodine 1811 B. Courtois 1811 B. Courtois Courtois discovered it in the ashes of seaweed.^[117] The name iode was given in French by Gay-Lussac and published in 1813.^[52] Davy gave it the English name iodine in 1814.^[52] 3 Lithium 1817 A. Arfwedson 1821 W. T. Brande Arfwedson, a student of Berzelius, discovered the alkali in petalite.^[118] Brande isolated it electrolytically from lithium oxide.^[52] 48 Cadmium 1817 S. L Hermann, F. Stromeyer, and J.C.H. Roloff 1817 S. L Hermann, F. Stromeyer, and J.C.H. Roloff All three found an unknown metal in a sample of zinc oxide from Silesia, but the name that Stromeyer gave became the accepted one.^[119] 34 Selenium 1817 J. Berzelius and G. Gahn 1817 J. Berzelius and G. Gahn While working with lead they discovered a substance that they thought was tellurium, but realized after more investigation that it was different.^[120] 35 Bromine 1825 J. Balard and C. Löwig 1825 J. Balard and C. Löwig They both discovered the element in the autumn of 1825. Balard published his results the next year,^[121] but Löwig did not publish until 1827.^[122] 90 Thorium 1829 J. Berzelius 1914 D. Lely, Jr. and L. Hamburger Berzelius obtained the oxide of a new earth in thorite.^[123] 57 Lanthanum 1838 G. Mosander 1841 G. Mosander Mosander found a new element in samples of ceria and published his results in 1842, but later he showed that this lanthana contained four more elements.^[124] 60 Neodymium 1841 G. Mosander 1885 C. A. von Welsbach Discovered by Mosander and called didymium. Carl Auer von Welsbach later split it into two elements, praseodymium and neodymium. Neodymium had formed the greater part of the old didymium and received the prefix "neo-".^[85][125] 68 Erbium 1843 G. Mosander 1879 T. Cleve Mosander managed to split the old yttria into yttria proper and erbia, and later terbia too.^[126] The names underwent some confusion: Mosander's erbia was yellow and his terbia was red. But in 1860, Nils Johan Berlin could only find the rose-coloured earth, confusingly renamed as erbia, and questioned the existence of the yellow earth. Marc Delafontaine adopted Berlin's nomenclature where erbia was the rose-coloured earth, but proved that the yellow earth also existed. At the prompting of Jean Charles Galissard de Marignac, he named the yellow earth terbia; thus Mosander's names were swapped from his original choices.^[52] 65 Terbium 1843 G. Mosander 1886 J.C.G. de Marignac Mosander managed to split the old yttria into yttria proper and erbia, and later terbia too.^[127] 44 Ruthenium 1844 K. Claus 1844 K. Claus Gottfried Wilhelm Osann thought that he found three new metals in Russian platinum samples in 1826, which he named polinium, pluranium, and ruthenium in 1828. But his results were questioned and he did not have enough quantities to isolate them, so he withdrew his claims in 1829.^[128] However, in 1844 Karl Karlovich Klaus confirmed that there was one new metal, and reused Osann's name "ruthenium".^[129] 55 Caesium 1860 R. Bunsen and R. Kirchhoff 1882 C. Setterberg Bunsen and Kirchhoff were the first to suggest finding new elements by spectrum analysis. They discovered caesium by its two blue emission lines in a sample of Dürkheim mineral water.^[130] The pure metal was eventually isolated in 1882 by Setterberg.^[131] 37 Rubidium 1861 R. Bunsen and G. R. Kirchhoff 1863 R. Bunsen Bunsen and Kirchhoff discovered it just a few months after caesium, by observing new spectral lines in the mineral lepidolite.^[132] The metal was isolated by Bunsen around 1863.^[52] 81 Thallium 1861 W. Crookes 1862 C.-A. Lamy Shortly after the discovery of rubidium, Crookes found a new green line in a selenium sample; later that year, Lamy found the element to be metallic.^[133] 49 Indium 1863 F. Reich and T. Richter 1864 T. Richter Reich and Richter first identified it in sphalerite by its bright indigo-blue spectroscopic emission line.^[134] Richter isolated the metal the next year.^[52] 2 Helium 1868 N. Lockyer 1895 W. Ramsay, T. Cleve, and N. Langlet P. Janssen and Lockyer observed independently a yellow line in the solar spectrum that did not match any other element. However, only Lockyer made the correct conclusion that it was due to a new element. This was the first observation of a noble gas, located in the Sun. Years later after the isolation of argon on Earth, Ramsay, Cleve, and Langlet observed independently helium trapped in cleveite.^[135] 1869 D. I. Mendeleev Mendeleev arranges the 63 elements known at that time (omitting terbium, as chemists were unsure of its existence, and helium, as it was not found on Earth) into the first modern periodic table and correctly predicts several others. 31 Gallium 1875 P. E. L. de Boisbaudran 1878 P. E. L. de Boisbaudran and E. Jungfleisch Boisbaudran observed on a pyrenea blende sample some emission lines corresponding to the eka-aluminium that was predicted by Mendeleev in 1871. He and Jungfleisch isolated the metal three years later by electrolysis.^{[136][137][52]} 70 Ytterbium 1878 J.C.G. de Marignac 1906 C. A. von Welsbach On 22 October 1878, Marignac reported splitting terbia into two new earths, terbia proper and ytterbia.^[138] 67 Holmium 1878 J.-L. Soret and M. Delafontaine 1879 T. Cleve Soret found it in samarskite and later, Per Teodor Cleve split Marignac's erbia into erbia proper and two new elements, thulium and holmium. Delafontaine's philippium turned out to be identical to what Soret found.^[139][140] 21 Scandium 1879 F. Nilson 1879 F. Nilson Nilson split Marignac's ytterbia into pure ytterbia and a new element that matched Mendeleev's 1871 predicted eka-boron.^[141] 69 Thulium 1879 T. Cleve 1879 T. Cleve Cleve split Marignac's erbia into erbia proper and two new elements, thulium and holmium.^[142] 62 Samarium 1879 P.E.L. de Boisbaudran 1879 P.E.L. de Boisbaudran Boisbaudran noted a new earth in samarskite and named it samaria after the mineral.^[143] 64 Gadolinium 1880 J. C. G. de Marignac 1886 P.E.L. de Boisbaudran Marignac initially observed the new earth in terbia, and later Boisbaudran obtained a pure sample from samarskite.^[144] 59 Praseodymium 1885 C. A. von Welsbach Carl Auer von Welsbach discovered it in Mosander's didymia.^[145] 32 Germanium 1886 C. A. Winkler In February 1886 Winkler found in argyrodite the eka-silicon that Mendeleev had predicted in 1871.^[146] 66 Dysprosium 1886 P.E.L. de Boisbaudran 1905 G. Urbain De Boisbaudran found a new earth in erbia.^[147] 18 Argon 1894 Lord Rayleigh and W. Ramsay 1894 Lord Rayleigh and W. Ramsay They discovered the gas by comparing the molecular weights of nitrogen prepared by liquefaction from air and nitrogen prepared by chemical means. It is the first noble gas to be isolated.^[148] 63 Europium 1896 E.-A. Demarçay 1901 E.-A. Demarçay Demarçay found spectral lines of a new element in Lecoq's samarium, and separated this element several years later.^[149] 36 Krypton 1898 W. Ramsay and W. Travers 1898 W. Ramsay and W. Travers On May 30, 1898, Ramsay separated a noble gas from liquid argon by difference in boiling point.^[150] 10 Neon 1898 W. Ramsay and W. Travers 1898 W. Ramsay and W. Travers In June 1898 Ramsay separated a new noble gas from liquid argon by difference in boiling point.^[150] 54 Xenon 1898 W. Ramsay and W. Travers 1898 W. Ramsay and W. Travers On 12 July 1898, Ramsay separated a third noble gas within three weeks, from liquid argon by difference in boiling point.^[151] 84 Polonium 1898 P. and M. Curie 1946 In an experiment done on 13 July 1898, the Curies noted an increased radioactivity in the uranium obtained from pitchblende, which they ascribed to an unknown element. Independently rediscovered and isolated in 1902 by Marckwald, who named it radiotellurium.^[152] Pure polonium was obtained in 1946.^[153] 88 Radium 1898 P. and M. Curie 1910 Marie Curie and André-Louis Debierne The Curies reported on 26 December 1898, a new element different from polonium, which Marie later isolated from uraninite.^[154] In September 1910, Marie Curie and André-Louis Debierne announced that they had isolated radium as a pure metal.^[155][156] 86 Radon 1899 E. Rutherford and R. B. Owens 1910 W. Ramsay and R. Whytlaw-Gray Rutherford and Owens discovered a radioactive gas resulting from the radioactive decay of thorium, isolated later by Ramsay and Gray. In 1900, Friedrich Ernst Dorn discovered a longer-lived isotope of the same gas from the radioactive decay of radium. Since "radon" was first used to specifically designate Dorn's isotope before it became the name for the element, he is often mistakenly given credit for the latter instead of the former.^[157][158] 89 Actinium 1902 F. O. Giesel 1903 F. O. Giesel Giesel obtained from pitchblende a substance that had properties similar to those of lanthanum and named it emanium.^[159] André-Louis Debierne had previously (in 1899 and 1900) reported the discovery of a new element actinium that was supposedly similar to titanium and thorium, which cannot have included much actual element 89. But by 1904, when Giesel and Debierne met, both had radiochemically pure element 89, and so Debierne has generally been given credit for the discovery.^[160] 71 Lutetium 1906 C. A. von Welsbach and G. Urbain 1906 C. A. von Welsbach von Welsbach proved that the old ytterbium also contained a new element, which he named cassiopeium (he renamed the larger part of the old ytterbium to aldebaranium). Urbain also proved this at about the same time (von Welsbach's paper was published first, but Urbain sent his to the editor first), naming the new element lutetium and the old one neoytterbium (which later reverted to ytterbium). However, Urbain's samples were very impure and only contained trace quantities of the new element. Despite this, his chosen name lutetium was adopted by the International Committee of Atomic Weights, whose membership included Urbain. The German Atomic Weights Commission adopted cassiopeium for the next forty years. Finally in 1949 IUPAC decided in favour of the name lutetium as it was more often used.^[85][161] 75 Rhenium 1908 M. Ogawa 1908 M. Ogawa Masataka Ogawa found it in thorianite in 1908, but assigned it as element 43 and named it nipponium. (Elements 43 and 75 are in the same group of the periodic table.)^[162] Because of the erroneous assignment, and because some of his key results were published only in Japanese, his claim was not widely recognised. However, the optical emission spectrum described by Ogawa and the X-ray photographic plate for one of his samples match element 75, and his claim has thus been rehabilitated in much of the modern literature.^[163] In 1925 Walter Noddack, Ida Eva Tacke and Otto Berg announced its separation from gadolinite, identified it correctly as element 75, and gave it the present name.^[164][165] 91 Protactinium 1913 O. H. Göhring and K. Fajans 1927 A. von Grosse The two obtained the first isotope of this element, ^234mPa, that had been predicted by Mendeleev in 1871 as a member of the natural decay of ²³⁸U: they named it brevium. A longer-lived isotope ²³¹Pa was found in 1918 by Otto Hahn and Lise Meitner, and was named by them protoactinium: since it is longer-lived, it gave the element its name. Protoactinium was changed to protactinium in 1949.^[166] Originally isolated in 1900 by William Crookes, who nevertheless did not recognize that it was a new element.^[167] 72 Hafnium 1922 D. Coster and G. von Hevesy 1924 Anton Eduard van Arkel and Jan Hendrik de Boer Georges Urbain claimed to have found the element in rare-earth residues, while Vladimir Vernadsky independently found it in orthite. Neither claim was confirmed due to World War I, and neither could be confirmed later, as the chemistry they reported does not match that now known for hafnium. After the war, Coster and Hevesy found it by X-ray spectroscopic analysis in Norwegian zircon.^[168] Anton Eduard van Arkel and Jan Hendrik de Boer were the first to prepare metallic hafnium by passing hafnium tetraiodide vapor over a heated tungsten filament in 1924.^[169][170] Hafnium was the last stable element to be discovered (noting however the difficulties regarding the discovery of rhenium). 43 Technetium 1937 C. Perrier and E. Segrè 1937 C. Perrier & E. Segrè The two discovered a new element in a molybdenum sample that was used in a cyclotron, the first element to be discovered by synthesis. It had been predicted by Mendeleev in 1871 as eka-manganese.^{[171][172][173]} In 1952, Paul W. Merrill found its spectral lines in S-type red giants.^[174] Minuscule trace quantities were finally found on Earth in 1962 by B. T. Kenna and Paul K. Kuroda: they isolated it from Belgian Congo pitchblende, where it occurs as a spontaneous fission product of uranium.^[175] The Noddacks (rediscoverers of rhenium) claimed to have discovered element 43 in 1925 as well and named it masurium (after Masuria), but their claims were disproven by Kuroda, who calculated that there cannot have been enough technetium in their samples to have enabled a true detection.^[176] 87 Francium 1939 M. Perey Perey discovered it as a decay product of ²²⁷Ac.^[177] Francium was the last element to be discovered in nature, rather than synthesized in the lab, although four of the "synthetic" elements that were discovered later (plutonium, neptunium, astatine, and promethium) were eventually found in trace amounts in nature as well.^[178] Before Perey, it is likely that Stefan Meyer, Viktor F. Hess, and Friedrich Paneth had observed the decay of ²²⁷Ac to ²²³Fr in Vienna in 1914, but they could not follow up and secure their work because of the outbreak of World War I.^[178] 93 Neptunium 1940 E.M. McMillan and H. Abelson Obtained by irradiating uranium with neutrons, it was the first transuranium element discovered.^[179] Shortly before that, Yoshio Nishina and Kenjiro Kimura discovered the uranium isotope ²³⁷U and found that it beta decays into ²³⁷93, but were unable to measure the activity of the element 93 product because its half-life was too long. McMillan and Abelson succeeded because they used ²³⁹U, as ²³⁹93 has a much shorter half-life.^[180] McMillan and Abelson found that ²³⁹93 itself undergoes beta decay and must produce an isotope of element 94, but the quantities they used were not enough to isolate and identify element 94 along with 93.^[181] Natural traces were found in Belgian Congo pitchblende by D. F. Peppard et al. in 1952.^[182] 85 Astatine 1940 D. R. Corson, K. R. MacKenzie and E. Segrè Obtained by bombarding bismuth with alpha particles.^[183] In 1943, Berta Karlik and Traude Bernert found it in nature; due to World War II, they were initially unaware of Corson et al.'s results.^[184] Horia Hulubei and Yvette Cauchois had previously claimed its discovery as a natural radioelement from 1936, naming it dor: they likely did have the isotope ²¹⁸At, and probably did have enough sensitivity to distinguish its spectral lines. But they could not chemically identify their discovery, and their work was doubted because of an earlier false claim by Hulubei to having discovered element 87.^[185][186] 94 Plutonium 1941 Glenn T. Seaborg, Arthur C. Wahl, W. Kennedy and E.M. McMillan Prepared by bombardment of uranium with deuterons.^[187] Seaborg and Morris L. Perlman then found it as traces in natural Canadian pitchblende in 1941–1942, though this work was kept secret until 1948.^[188] 96 Curium 1944 Glenn T. Seaborg, Ralph A. James and Albert Ghiorso Prepared by bombarding plutonium with alpha particles during the Manhattan Project^[189] 95 Americium 1944 G. T. Seaborg, R. A. James, O. Morgan and A. Ghiorso Prepared by irradiating plutonium with neutrons during the Manhattan Project.^[190] 61 Promethium 1945 Charles D. Coryell, Jacob A. Marinsky, and Lawrence E. Glendenin 1945 Charles D. Coryell, Jacob A. Marinsky, and Lawrence E. Glendenin^[191][192] It was probably first prepared at the Ohio State University in 1942 by bombarding neodymium and praseodymium with neutrons, but separation of the element could not be carried out. Isolation was performed under the Manhattan Project in 1945.^[193] Found on Earth in trace quantities by Olavi Erämetsä in 1965; so far, promethium is the most recent element to have been found on Earth.^[194] 97 Berkelium 1949 G. Thompson, A. Ghiorso and G. T. Seaborg (University of California, Berkeley) Created by bombardment of americium with alpha particles.^[195] 98 Californium 1950 S. G. Thompson, K. Street, Jr., A. Ghiorso and G. T. Seaborg (University of California, Berkeley) Bombardment of curium with alpha particles.^[196] 99 Einsteinium 1952 A. Ghiorso et al. (Argonne Laboratory, Los Alamos Laboratory and University of California, Berkeley) Formed in the first thermonuclear explosion in November 1952, by irradiation of uranium with neutrons; kept secret for several years.^[197] 100 Fermium 1953 A. Ghiorso et al. (Argonne Laboratory, Los Alamos Laboratory and University of California, Berkeley) Formed in the first thermonuclear explosion in November 1952, by irradiation of uranium with neutrons; first identified in early 1953; kept secret for several years.^[198] 101 Mendelevium 1955 A. Ghiorso, G. Harvey, G. R. Choppin, S. G. Thompson and G. T. Seaborg (Berkeley Radiation Laboratory) Prepared by bombardment of einsteinium with alpha particles.^[199] 103 Lawrencium 1961 A. Ghiorso, T. Sikkeland, E. Larsh and M. Latimer (Berkeley Radiation Laboratory) First prepared by bombardment of californium with boron atoms.^[200] 102 Nobelium 1965 E. D. Donets, V. A. Shchegolev and V. A. Ermakov (JINR in Dubna) First prepared by bombardment of uranium with neon atoms^[201] 104 Rutherfordium 1969 A. Ghiorso et al. (Berkeley Radiation Laboratory) and I. Zvara et al. (JINR in Dubna) Prepared by bombardment of californium with carbon atoms by Albert Ghiorso's team and by bombardment of plutonium with neon atoms by Zvara's team.^[202] 105 Dubnium 1970 A. Ghiorso et al. (Berkeley Radiation Laboratory) and V. A. Druin et al. (JINR in Dubna) Prepared by bombardment of californium with nitrogen atoms by Ghiorso's team and by bombardment of americium with neon atoms by Druin's team.^[203] 106 Seaborgium 1974 A. Ghiorso et al. (Berkeley Radiation Laboratory) Prepared by bombardment of californium with oxygen atoms.^[204] 107 Bohrium 1981 G.Münzenberg et al. (GSI in Darmstadt) Obtained by bombarding bismuth with chromium.^[205] 109 Meitnerium 1982 G. Münzenberg, P. Armbruster et al. (GSI in Darmstadt) Prepared by bombardment of bismuth with iron atoms.^[206] 108 Hassium 1984 G. Münzenberg, P. Armbruster et al. (GSI in Darmstadt) Prepared by bombardment of lead with iron atoms^[207] 110 Darmstadtium 1994 S. Hofmann et al. (GSI in Darmstadt) Prepared by bombardment of lead with nickel^[208] 111 Roentgenium 1994 S. Hofmann et al. (GSI in Darmstadt) Prepared by bombardment of bismuth with nickel^[209] 112 Copernicium 1996 S. Hofmann et al. (GSI in Darmstadt) Prepared by bombardment of lead with zinc.^[210][211] 114 Flerovium 1999 Y. Oganessian et al. (JINR in Dubna) Prepared by bombardment of plutonium with calcium. It may have already been found at Dubna in 1998, but that result has not been confirmed.^[212] 116 Livermorium 2000 Y. Oganessian et al. (JINR in Dubna) Prepared by bombardment of curium with calcium^[213] 118 Oganesson 2002 Y. Oganessian et al. (JINR in Dubna) Prepared by bombardment of californium with calcium^[214] 115 Moscovium 2003 Y. Oganessian et al. (JINR in Dubna) Prepared by bombardment of americium with calcium^[215] 113 Nihonium 2003–2004 Y. Oganessian et al. (JINR in Dubna) and K. Morita et al. (RIKEN in Wako, Japan) Prepared by decay of moscovium by Oganessian's team^[215] and bombardment of bismuth with zinc by Morita's team.^[216] Both teams began their experiments in 2003; Oganessian's team detected its first atom in 2003, but Morita's only in 2004. However, both teams published in 2004. 117 Tennessine 2009 Y. Oganessian et al. (JINR in Dubna) Prepared by bombardment of berkelium with calcium^[217]